Gear Review: CMC Triggers Drop-In AR-15 Trigger

Next up in the series of AR-15 drop-in triggers for review is the flat trigger unit from CMC Triggers. This trigger pack has represented the lowest-cost, drop-in option on the market for many years, only outseated recently as the budget leader by the Velocity Trigger. Let’s dive in and see how it stacks up on features and fundamentals . . .

MSRP comes in at $189.99, and it’s widely available online for about $167.

I’ve been describing the build of the trigger units to far — materials, finish, machining process, etc — but CMC is pretty vague on its website. The information available is:

Tolerances of +/- .001″ for all engagement surfaces.

Hammer, trigger, disconnector and pins are made with the highest grade, hardest, longest-wearing materials available.

The assembly is contained in a high-grade 410 stainless steel housing.

Full-strength rocket wire springs for fast lock-time and reliable discharge with factory or military ammo (not recommended for use in 5.45×39).

It’s worth noting that this is the only drop-in trigger unit on the market that isn’t contained within a CNC machined housing. Wilson Combat’s drop-ins are housed in a block of machined billet steel, and the rest of them are housed in billet aluminum. I actually like CMC’s idea of using a piece of sheet metal bent into shape. Quick, easy, sufficiently effective, and definitely low cost. But as CMC is no longer king of the budget hill, it looks less appealing.

Obviously I can’t actually say what sort of steel the FCG parts are made from, or how they’re machined. In this day of wire EDM machining, though, tolerances of one thousandth actually seem loose.

Many of the other manufacturers flaunt the fact that they use full 1/4″ width disconnectors. I’m not sure I’m likely to put enough rounds through a trigger to prove or deny the claim of additional durability from that increased engagement surface, but have brought it up thus far so it’s worth mentioning that the CMC unit employs a rather skinny hammer and a very skinny disco.

Pull weight is set at the factory. There is a 3.5, 4.5, 5.5, and 6.5 lb option, with each available in curved or straight trigger shoe flavor. My example is a 3.5-lb unit, and my Timney trigger pull gauge pegs it at a very consistent 2.75 lbs. Pre- and over-travel are also taken care of at the factory, so the only thing remaining is to drop it in and go shooting.

Unfortunately, CMC Triggers’ triggers lack one feature that I definitely value — a means by which to tension the unit inside of the receiver. Although this ends up being a fairly small nitpick in practice, if you check out the video above you’ll be able to see and hear how the trigger pack wiggles inside the receiver. As they really must be to account for receiver and trigger pack tolerances, the bushings in the trigger unit through which the trigger pins go are slightly larger in inner diameter than the pins are in outer diameter. With no way to clamp the trigger unit down, it wiggles on the pins. It’s the only drop-in trigger on the market, at least as far as I know, that doesn’t attempt to take up this slack somehow. If this were my trigger, I’d put tape under the rear of the housing until it had to be compressed with a few pounds of force before the trigger pin could get through.

On The Range
To maintain continuity across all of these drop-in trigger reviews, including the ELF review and Velocity review already published, we’ll rate them on the same metrics. For definitions of the following trigger fundamentals, please see that ELF Tactical review.

Take-up, which is also referred to as pre-travel or slack. The trigger itself has no take-up. It’s a single stage and it’s right up on the sear at rest. However, it may or may not have rearwards wiggle room depending on how it’s positioned on the pins. That click can feel like a millimeter of take-up.

Creep. Most of the time, there was no detectable creep in this trigger at all. A few times, a hint of creep was detectable and visible. A little awkward that it wasn’t totally consistent, but it’s still like 99.5% flawless here.

Break. Possibly due to the pull weight of only 2.75 lbs on my example, the break has a light feel to it. However, it’s pretty dang crisp and very nice. It goes from 2.75 lbs to 0 instantaneously, and that’s what we’re looking for.

Overtravel. Short, but room for improvement. It’s pretty solid at the back, but doesn’t have the same steel-on-steel feel of some others.

Reset. Smooth trigger travel forwards to a click that is on the light side but still audible and tactile. There were a couple of instances where it felt like it caught at the end — like the disconnector didn’t want to let go — but only when I was releasing the trigger in an exaggeratedly slow manner to get a feel for it.

Pull Weight. Plenty of options from the factory, although the 3.5 lb and 4.5 lb ones seem to be most commonly stocked by retailers. I’ve seen the 3.5 lb one advertised as “3.0 to 3.5 lb,” but, again, mine measured a totally consistent 2.75 lbs.

I shot some IMI 5.56, Federal 5.56, and a bunch of Silver Bear .223 with the CMC trigger installed, and it had no issues with any of it. Despite their fairly hard primers, they had acceptable dents. The trigger was totally reliable for me throughout, both suppressed and unsuppressed.

The look of CMC’s flat trigger blade may be a little extreme, and I’ve seen folks express concern about how it might feel with that hook on the bottom, but I’m happy to report that in practice it feels great. That hook or flange causes no discomfort whatsoever, and it has the benefit of providing an index point for your index finger. A couple other triggers on the market employ similar — if not more visually-pronounced — methods of ensuring consistent trigger finger placement, as this fosters accurate, consistent shooting.

Thanks to a much cleaner break, lower pull weight, and less overall travel with none of the grit, the CMC unit is significantly faster than a mil-spec trigger. It’s also easier to shoot it accurately, whether shooting quickly or making slow, precise shots from a rest.

Conclusion
The CMC trigger is good enough that if it shipped in a rifle I bought, I wouldn’t replace it. That said, with the entry of the Velocity Trigger to the market, I can’t see spending more money on the CMC since it has fewer features, lower build quality, and falls just short of the Velocity on trigger pull fundamentals. It doesn’t quite have the same crisp, solid feel. It’s really dang good! But it’s a bit softer around the edges.

Bottom line for me is that the CMC needs to once again claim the title of least expensive drop-in trigger. It would still be a solid choice at the right price. Conversely, some changes to build and features could make it more competitive at its current price. It’s still a known quantity and a popular trigger and there’s a lot of inertia there, but it’s roundly beaten in every last category by Velocity’s unit.

RATINGS (out of five stars, compared to other drop-in AR triggers):

Fundamentals * * *
Average or even slightly above average for this group of drop-ins. No creep and a nice break.

Features *
The only drop-in of 10 that doesn’t attempt to eliminate wiggle in the receiver. No other adjustments are available either. Skinny hammer and disconnector. Sheet metal housing.

Overall * *
Price would be the redeeming factor here, and if it were the least expensive option by a decent margin I could be convinced to rate it above average. However, a better trigger is readily available for $40 less. To be clear, in comparison to the entire AR-15 trigger market and certainly in comparison to a mil-spec trigger, the CMC drop-in is great. This rating is against the other 8 drop-in triggers that I have here, where it’s slightly above average on fundamentals but has the lowest build quality, least features, etc. It’s just outclassed in this specific group, so comes in just below average overall.

comments

People who think a 0.001″ tolerance is “loose” have never tried to measure anything to that spec. To keep that tolerance, you need an inspection system at least ten times that accurate (0.0001″). Realistically speaking, for something like that, you’re looking at a $120,000 CMM or a $60,000 scope.

Typical EDM tolerance for single pass is more like 0.0002″ and it can get way down from there with further runs. I was mostly just surprised to see 0.001″ bragged about in a sea of competitors holding tolerances at least 5x tighter. BTW, you may note in one of the photos above (pic of the inside w/ the hammer down) that the bottom of the hammer hasn’t worn perfectly evenly. Tolerances on a hammer & sear surface are pretty dang important. The wear from the trigger (sear) dragging on the hammer is even on the other triggers I’ve put enough rounds through to induce finish wear.

I hear EDM guys keep bragging about that 5 micron (~0.0002″) “tolerance” but every time I go to inspect their work with one of my scopes… Not so much. A machine that can seriously hold a few micron tolerances should be leaving a mirror finish when it’s done. Most people forget just how small a thousandth or ten-thousandth of an inch really is.

“Loose” specs are always a matter of context. In the overwhelming majority of applications, 0.001″ is fine, if not overly tight. In others, you might as well chuck it in the trash if tolerances are that loose (think telescope mirrors). In this case, it matters because the trigger pack wobbles in the receiver, and that happens because the tolerances of the receiver and the stamped metal parts result in gaps. As a designer you know ahead of time that this is going to happen because you are designing to make sure it fits in EVERY receiver regardless of where it falls within the spec limits, so the absence of a way to deal with it is a little poor.

Not necessarily the same thing. You’re talking clearances, not tolerances. A system can have very tight tolerances and still wobble all over the place. That wobble may be part of the design to accommodate proper function in adverse conditions.

The rule I give engineers when I deal with them. Every time you want to add a zero to your tolerance, add a zero to the cost of your inspection system.

I agree with none of the conclusions, andA I would rate it at a 3.5 to 4 stars overall. There is a bit of wiggle but that can EASILY be taken care of with aluminum/steel or plastic shim material for PENNIES if it’s a huge issue for someone.
Now, to the most glaring issue I have with the article: Yes you can get a Velocity trigger unit for about $110 shipped BUT the quality , fit and finish is FAR lacking. The ones I’ve seen look like some cheap Chinese made knock off crap. The things look like some kid cut the parts out with a cheap plasma cutter in his mom’s basement. This comparison only works when comparing these two by price alone. The Velocity trigger is expensive at $99 when you look at the parts and their fit/finish. CMC would be cutting their own throats by trying to bring their prices down to match. I wouldn’t take THREE Velocity triggers for one CMC. The one I have fits well with no noticeable “wiggle”, it is smooth as glass and has a crisp break and smooth reset. For approximately $160 it’s unbeatable in its class.
My conclusion: if PRICE is the main factor in your purchase of AR triggers, then the Velocity is for you. If QUALITY and PERFORMANCE are the biggest factors yet you need to be “budget conscious”…get the CMC. I have one in my “plinker” SBR and I wouldn’t take for it….I wanted a good single stage with a light pull but couldn’t justify $300 for a “beater” AR. Didn’t want some kind of junk in it either so CMC was a cinch…and once I fired it, I was sold on them for their simple yet rugged construction.
(I did not get paid, offered gifts or get promised any kind of compensation to say any of this. I am simply impressed by the trigger and everybody else that I know that has one or more feels the same way).

You must be thinking of a different Velocity Trigger. The quality is better than CMC (and many of the other drop-in options, for that matter) in every last way. The wire EDM machining is more precise, the hardened american tool steel is likely higher quality, the Robar NP3 coating is slick and awesome, the CNC machined, anodized aluminum chassis is flawless in machining and finish. Even the bushings and springs look better. I can see visible machine marks on the CMC fire control parts.

Again, I think the CMC is fine and it’s a very good trigger in its own right. Only compared against the rest of the drop-in trigger market does it come up below average. But your comments on quality of the Velocity are WAY off base and have nothing to do with reality at all.

This review is going to get torn up in the comments. As mentioned, the CMC has been extremely popular for years. There’s a lot of inertia there. A lot of people who have spent hard-earned money on one. You know how defensive folks get about defending their choices, the way they spent money, which caliber they committed to, etc 😉 . This review should not be insulting to those folks and it should not be insulting to CMC. It’s a GREAT trigger. It’s just below average vs. the drop-in market. I have Wilson Combat, ELF Tactical, Velocity Triggers, POF, BRO, RISE Armament, KE Arms, and Timney here right now. I hope to add American Trigger. This is all of the drop-ins on the market that I know of (discounting Tac-Con). The CMC is below average. Period. Were the Velocity not available now and the CMC were still the low price champion, it would rate at least a star higher. Two stars doesn’t mean bad, it means below average (3 = average). In this group of 9 or 10 drop-ins, they can’t all be above average… and the CMC isn’t.

Have you tried one? I thought it looked really goofy, and just fiddling with it, it did not feel as nice as that lovely curve. But shooting it changed my mind, just as Jeremy mentioned, the shape allows, maybe forces you to put your finger in the same place each time, and the weight is so light that you don’t notice the shape while actually firing. Kind of an eye-opener.

I’m surprised you didnt spend any time talking about their absolutely horrible mounting system. C-clips and small screws sticking out the side of the receiver? Are you kidding me? I didnt watch the video so maybe you did there. I bought one of these once and gave it away. The actual pull of the trigger wasn’t bad but man that whole thing wiggled around so much in my lower I absolutely couldn’t believe anyone would buy one.

Most of the leading anti-walk trigger pin kits on the market use screws. KNS, for example, uses little torx bolts and is the go-to for many rifle and trigger manufacturers (in fact, I think 3 of the 9 drop-in units I have came with KNS pins). The C-clips are less confidence-inspiring but they do work just fine.

Ive got a few thousand rounds through mine and set up two other friends with this trigger as well. No failures, works great for the money, and is reliable. Sure it may not be as nice as the “best” ones out there and have a little more wiggle/creep but its price point easily makes it 4 stars for overall.

This is a cheap, reliable, easy to install trigger that makes shooting so much nicer. You removed points under features because you just didn’t like the way it looked. Even with it working perfectly.

That’s right. 3 stars is average. I have all of the drop-in triggers on the market here, less the AR Gold, and have shot and played with all of them. In this group, the CMC is below average. As mentioned, price would bump it up to a higher rating but it’s roundly beaten by a better trigger that’s $40 less.

I removed points from features primarily because it lacks zero features in a market where ALL of the others have at least one. Mainly, a feature that keeps it snug in the receiver. Some have that plus trigger pull weight adjustment. Some have additional safety features like half cock notches. Some are adjustable for overtravel. Most have full-width hammers and disconnectors (which means more sear and disconnector/hammer engagement surface). These are all features lacking on the CMC. In this crowd of drop-in AR triggers, it is the bottom of the market on features. Objectively, not subjectively. It just is.

They’re all reliable. They’re all drop-ins so they’re all easy to install. Compared to mil-spec I’d give the CMC 5 stars. It’s being compared to its peers, though, meaning other drop-in units, and in this group it’s just below average.

I dunno, I have this exact trigger in my AR pistol, and it’s awesome. No “wiggle”, no issues whatsoever. I’ve put thousands of rounds though it and never had a trigger-related problem. I guess I got lucky or something.

No, not lucky and I wouldn’t disagree with you. I don’t expect any problems from it and it’s a very good trigger. As mentioned, if it came in a gun I bought I wouldn’t replace it, and I wouldn’t expect to ever shoot enough rounds through it that the narrow disconnector or hammer/sear would likely matter. It’s still below average compared to the other drop-ins, though. Mostly because they’re all so stellar. This trigger is awesome… right up until you play with it next to the other drop-in options, where it’s still very solid on trigger pull fundamentals but falls short elsewhere.

Got it! Thanks for that. I’ve only ever used the CMC drop-ins, so I don’t know the difference. For my long guns with glass I used the Geissele SSAE for the trigger group, so I appreciate your comments explaining the bigger picture. I guess if I ever put another pistol together I’ll probably end up using the velocity, sounds like.
Thanks again!

Great review, Jeremy. I had no idea the CMC trigger was stamped, guess I never really paid attention the description until now. I had almost ruled it out because of the pull weights offered, but looks like it won’t be making the cut now.

Love my cmc 3.5 drop in trigger. Mine is just the regular curved trigger and it has been great! Granted I got my trigger in a bundle deal and ended up selling the stock with the bundle so I came out only paying $7 dollars for the trigger.

This was my first choice for he rifle I built a year ago–until I ran over budget. I picked it for the trigger pull and weight as competitive to the high end triggers that ran $100 more.
Being price conscious, and with the added features, I’d opt for the Velocity today. I doubt the housing makes much of a difference (stamped versus milled), or the width of the sear and hammer (you should look at the sear in a 1861 Colt Navy) but the NP3 does,as do the locking screws. However, I would have to discover the undiscoverable–how wide is it compared to the CMS? With a poly 80% lower, I would likely have to make the FC pocket significantly wider, and that could be an issue.

They’re all the same width, as the FC pocket is a standard size and every receiver is milled to the same specification (or at least is supposed to be). Any trigger designed to go in an AR-15 should be the same width +/- manufacturing tolerance.

I have both the CMC and a Timney AR-15 Competition triggers. Honestly other than how pretty the Timney looks, the CMC felt exactly the same in terms of performance. I will be looking forward to your review of the Timney because there are some similarities and I am curious if you will ding them like you did the CMC.

I’m trying to keep all of the reviews very consistent, so if there’s an aspect of the CMC that’s described here (such as disconnector width), you can expect it to be described in all of the other reviews as well.

I won’t rehash all I’ve posted in other trigger reviews that mentioned the CMCs, just a summary:

I own a small horde of CMCs, 3.5, 4.5, curved and straight (single stage only, not the newer two stage models). Since the first one I installed these have been my go-to for replacing the basic mil-spec trigger in any build that I start (irons and RDS, optics builds I use two-stage Geissele’s usually). After I tried a flat trigger version I’ve been buying exclusively those, and while they seem odd at first, after a bit they really seem to provide the most consistent finger placement I’ve ever had. Love ’em.

That said, I picked a Velocity to try it out and ended up getting 2nd one for another build. That tiny, not consistently repeatable bit of creep (sometimes I think it is only in my head) does not exist at all on the Velos and they just break sharp. Period.

Time will tell how they stand up to abuse. I’ve got thousands and thousands of rounds on the various CMCs that I have and they just never fail (note: tried one in a 15-22 and it doesn’t always lock back, but that thing seems to have xenophobic tendencies when it comes to any trigger I try in it).

“That tiny, not consistently repeatable bit of creep (sometimes I think it is only in my head)…”

I’ve felt the same way. The CMC isn’t totally consistent but it’s such a small thing that sometimes I think it’s in my head. It’s either creep that’s there sometimes but not usually, or it’s the reset feeling slow or otherwise weird. I think it’s wobble in the hammer/trigger on their respective pins, possibly combined with a loose tolerance on the hammer/sear engagement surfaces, and/or possibly combined with the thick axle grease that’s in there. Note that on the Velocity, which you mentioned as being consistent, there’s no lube at all. The NP3 coating provides inherent lubricity and Velocity’s FAQ says you shouldn’t even worry about lubing it… which is kind of cool since that means less carbon, dust, etc sticking to the surfaces.

“…note: tried one in a 15-22 and it doesn’t always lock back…”

A lot of aftermarket triggers have issues on .22 and 9mm because of differences in the bolt design. The bolts usually don’t push the hammer down as far, and if that corner of the hammer that actually contacts the bolt is lower than mil-spec and/or the mechanics of the trigger require it to be pushed down farther to catch the disco than mil-spec, it won’t reset.

I put 1.555 pins in my new CMC to keep it from moving and it wasn’t my lower.
I was disappointed with it.
So I sold it and bought a American Gold. Very Happy.
Have a Geissele that I’m very happy with also.

I picked up a cmc that has yet to be installed on a brand new build, wish I would have heard about velocity, but, I think I’ll be extremely happy with my purchase. I would imagine a piece of tape and anti rotational pins would be an effective remedy as someone else mentioned. I have a friend who wants a cassette type trigger for his first build, I’ll definitely mention velocity. The cmc reputation sounds to be excellent, and up until now I never heard of anyone with anything but a favorable review of the unit, I’ll keep it in consideration. I was looking for something middle of the road between being as rugged as , or at least close to as rugged as a milspec trigger, while being as user friendly and light as something like an adjustable trigger, the cmc 3.5 with a flat bow looked to be dead in the middle, no adjustments to worry about failing, and drop in fit. Anyone who has ever inserted a hammer spring upside down can probably attest, it can be pretty embarrassing, worse case being a home defense situation after fully servicing a rifle. One less thing to worry about with a one piece unit.

I can’t beleive I spent hours trying to figure out why the damn thing was wiggling around so much. Luckilly, this article from 3 years ago saved me more time+aggravation. What’s the point of having a trigger (that does break great) if it’s gonna wiggle around like some cheaply made, low end Chinaman special? Time for CMC to take their existing stock, drill a hole or 2 in the housing, and put some allen screws to hold it in place. I’ll be returning mine+putting the enhanced trigger back in until my (second) velocity gets through the mail.

Thanks for the review. I’m still happy I made the choice to get one, which by the way i ordered about two hours ago. LOL. I’m very interested in comparing it to my JMT Sabre and my POF flat blade. And yes, I am in love with the 3.5 lb. 🙂